Antifouling coating for metal structures.



I v p 7 I l jIBatented October lse3' arce.

GEORGE D. COLEMAN, OF BOSTON MASSACHUSETTS, ASSIGNOR, BY MESNE ASSIGNMENTS, TO COLEMAN SHIP COPPERING TION OF MAINE.

OOMPANY, A CORPORA- ANTIFOULING COATING FOR METAL STRUCTURES.

SPECIFICATION forming part of Letters Patent No. 741,769, dated October 20, 1903.

Application filed February 6, 1902. Serial No 92,857. (No specimens.)

ToaZZ whom it may concern:

Be it known that I, GE RGE D. CoLuMAN,a citizen of the United States, residing at Boston, in the county of Suffolk and State of 5 Massachusetts, ha v-e "In-tented certain new and useful Improvementsin Antifouling Coatings for Metal Structures; and I do hereby declare the following to be a full, clear, and exact description of the invention, such IO as will enable others skilledin theart to which it appertains to make and use the same,

The present invention relates to an improved antifouling coating for metal structures submerged in or exposed to the action I 5 of water, and particularly sea-water.

The object of the present invention is to improve antifouling coatings for the above class of structures, and to the above end it consists in the antifoulin g coating hereinafter described, and particularly defined in the claims.

In the patent granted to me September 17, 1901, No. 682,913, I described and claimed an antifouling coating for metal structures composed of a layer of paint, a layer of finelydivided insulating material, and a layer of copper, the layer of insulating material being preferably of mineral character,although vegetable material was also contemplated for 0 use in this connection. In the patent granted to me September 17, 1900, No. 682,914, I described and claimed an antifonling coating similar to thatof the above-mentioned patent in-which the insulating material is specific- 5 ally defined as a vegetable substance. The inventions of these patents contemplate the use of an insulating layer between the metal to be coated and the layer of copper which protects the surface from the attack of ma- '40 rine life in order elfec'tnally to prevent any electrolytic action between the copper and the metal to be coated in the presence of water, and particularly seawater. I have found that in general a vegetable insnlating'material is superior to mineral, and it is imperative, I believe, to the best embodiment of my invention that all the moisture should be expelled from such insulating material before the same is incorporated into the body of the antifouling coating, as the presence of the substance was in a fine and impalpable state thatit was with difficulty blown against the paint, not having sufficient-weight to cause it to overcome the resistance of the air'in passingfrom the blower to the painted 6 5 surface. As a consequence of this it is is quired that the blower shou? be held very close to the painted surface,an i the air becoming filled with dust hinders the operatorfrom being able to observe in a satisfactory manner the progress of the work. Furthermore, difficulty has been experienced in causing thefinely-divided vegetable substance to form an efficient union with the paint in order to hold them together, inasmuch as the surface of the particles of wood nothaving been prepared in any way to make them stick to the paint the union was sometimes inefficient.

According to the present invention I make an antifouling coating in accordance with the method of application described in my said patents, in which the insulating material is oiled comminuted wood. Any suitable wood sawdust coated orimpregnated with a dryingoil is within the scope of my invention. I 8 prefer for this purpose a hard-wood sawdust sifted to remove particles which would be excluded by sitting with a sixty-mesh sieve. This wood sawdust is preferably first dried to expel whatever moisture may be contained 0 therein, which may be accomplished in any desired way, preferably by passing it through an oven at a temperature below that at which the wood would char. After the wood sawdust has been dried it is steeped in a drying- 5 oil, preferably raw linseed-oil, mixed with a drier in the volumetric proportions of eight of oil to one of drier. Then from the wood sawdust is extracted in any suitable manner all the surplus oil. This is conveniently accom- I00 plished by placing the material in a centrifugal separator, whereby the surplus oil is separated from the wood, and only so much oil remains as has been absorbed by the wood.

The wood is now coated with a thin film of lead or other soft metal-such as tin, zinc, or copper-and preferably by placing the wood in a tumbler with finely-divided metallic lead, such, preferably, as would be obtained by sifting with a one-hundred-and-twentymesh sieve. The proportions of lead and wood put in the tumbler will preferably be thirtyfive pounds of comminuted lead to jseventy-five pounds of wood,and the tumblingv process is continued until the particles of wood have been coated with finely-divided metallic lead. In practice the particles of wood will be found to be coated with a thin film or layer of lead, which gives them weight and toughness. The oiling process makes the wood less liable to the absorption of moisture and consequent swelling of the coating in case of rupture of the surface due to contactwith flotsam or the like. The coated wood is then allowed to dry. Any suitablemeans may be employed for drying the wood; but I prefer to dry it in evaporating-pans, in which the wood is placed and frequently stirred, so that all of the particles shall be equally dried and so that they shall not adhere to each other. The drying may be accomplished by exposing the coated wood to the sun or wind. it des-ire.- Tr sprgg uctis ag in screened through an eighty-mesiieve, when it is ready for use in making my antifoulingmoating.

In order to prevent as much as possible the wood from being attacked by the water, I prefer to employ a waterproof paint as-the binding material for the. coating, and while in its broader aspects my invention contemplates the employment of any suitable paint or cement for this purpose I prefer to use a paint which is made of cement or paint substance formed by mixing red lead or litharge with a drying-oil to the consistency of putty and baking the same at a low temperature, which is mixed with a varnish preferably made of forty gallons of linseed-oil to one described is not exactly known to me.

- tain amount of oxygen.

hundred pounds of Zanzibar or kauri gum, which paint is dense, tough, and impervious to moisture.

' The composition of the paint made as above During the baking process the oil is exposed to the atmosphere, from which it absorbs a cer- It also absorbs a certain amount of oxygen from the red lead. In this way the oil is converted into a solid substance which may conveniently be termed oxidized oil. The red lead on parting with part of its oxygen is presumably converted to a certain extent into other oxids of lead. Part of the red lead, however, is unaffected. The resultant of this action upon the red lead after the baking process may be conveniently called partly-reducedred lead, since it retains to a large extent the characteristic of red lead, but contains less oxygen than before. In addition to these chemical'actions already described the oxidized oil and reduced red lead may enter more or less into a chemical combination. 'They form a very close mechanical union, since the red lead and the dried oil are not separately distinguishable, but form a solid dry mass which may be pulverized.

The coating will preferably be made in the following manner, although any convenient method. may be employed for making the same: I first clean the surface to be provided with the antifouling coating by scraping or scrubbing to present a clean surface to the paint to be applied. Ithen coat this surface with a layer of paint, preferably the abovedescribed waterproof paint, and before the paint has dried and while it is still moist or tacky I apply, by means of a blower or any other suitable means, the oiled wood, preferably coated with finelv-dilided metallic lead in the manner 3|bQ"'. dBSGIlbOd, which is projected against are surface of the paint and adheres thereto. Then the coating is allowed to become 'jioroughly dry and hard.- A second laye of paint, preferably the same as the first layer, is now applied, to which coating of' paint is then applied, by any suitable means, suchas a blower, a layer of comminut-ed or finely-divided copper, which adheres to the layer of paint. This layer of comminuted orfinely-divided copper is now rolled or burnished or hammered into the layer of paint while it is still moist or tacky and into the layer of insulating material, which layer will efiectively prevent any of the comminuted copper from coming in contact with'the metal to be coated, thus constituting an insulating medium between the metal to be coated and the comminuted copperand preventing to a greater or less extent electrolytic action between the two metals, which would result in corroding the metal of the structure. This rolling or hammering or burnishing of the comminutedcopper into thesecond layer of paint results in embedding or enveloping the copper in the paint and in driving the copper against or into the particles of vegetable material, by which means the particles of copper are afforded a tenacious hold upon the layer of" insulating material, so that they are securely supported by and attached to said layer. This coating may now be allowed to dry, and the surface I mil v miil i iwh particles of metallic copper embedded therein.

These fine particles of copper will take up the paint which has been brought to the surface between the particles of copper previously applied, and therolling or hammering or burnishing of this layer of copper will be sufficient to present a smooth surface of copper,

which will efficiently prevent the accumulation of marine growths thereon. In this preferred embodiment. of my invention it will not be necessary in ordiirgry work where extreme smoothness of surface such as would be desired for racing-yachts, is not desired to polish the surface with steel-wool or emerypaper or the like, as the same will present a substantially smooth clean surface of metallic copper.

It is to be understood that wherever in the claims I have used the Word copper to designate the antifouling metal I intend thereby to define and include any alloy of copper which when exposed to the action of water or moisture will become covered by the poisonous salts of copper.

Although the term red lead has been used in the claims, it is to be understood that the invention is not limited thereto, since other equivalent substances, such as litharge, may be substituted therefor without depar ture from the invention.

Having thus described my invention, I claim as new and desire to secure by Letters Patent of the United States 1. An antifouling coating for metal structures composed of a layer of paint, a layer of finely-divided oiled vegetable substance and a layer of comminuted copper, substantially as described.

2. An antifouling coating for metal struc tures composed of a layer of paint, a layer of finely-divided oiled and lead-coated vegetable substance, and a layerof comminuted copper,- substantially as described.

3. An antifouling coating for metal structures composed of a layer of paint, a layer of finely-divided .oiled and lead-surfaced comminuted wood embedded in a layer of paint, and a layer of comminuted copper driven in the layer of wood presenting a smooth surface closely studded with bare particles of copper, substantially as described. I

4. An antifouling coating for metal structures composed of a layer of paint, formed of cement or paint sti lbstnnnegonsisting of red lead mixed with wand baked at a low temperature,m1xed with a varnish,a layer of finely-dividedoiled vegetable insulating material embedded in the layer of paint and a layer of comminuted copper, substantially as described.

5. An antifouling coating for metal structures composed of a layer of paint, formed of cement or paint substance consisting of red lead mixed with a drying-oil and baked at a low temperature, mixed with a varnish,a layer of. finely-divided oiled lead-coated wood embedded in the layer of paint, a second layer of paint applied thereto, and a layer of comminuted copper embedded in the second layer of paint and prevented from contact with the metal upon which the coating is placed by means of the layer of insulating oiled and lead-coated wood'presenting a smooth surface closely studded with bare particles of opper, substantially as described.

6. An antifouling coating for metal ,sf-sasM tures composed of layegpf 351' Re s layer of finelydivided, oiled' vegetable substance, and

a layer of comminuted copper,.the said paint consisting of a mixture of varnish and a pulverized, homogeneous, amorphous compound of intimately-mingled anhydrous drying-oil and red lead, substantially as described.

7. An antifouliug coating for metal structures composed of a layer of paint, a layer of finely-divided oiled and lead-coated vegetable substance, and a layer of comminuted copper, the said paint consisting of a mixture of varnish and a pulverized homogeneous, amorphous compound of intimately-mingled anhydrous drying-oil and partly-reduced red load, substantially as describe In testimony whereof I affix my signature in presence of two witnesses.

GEORGE D. COLEMAN.

Witnesses:

HORACE VAN EVEREN, BENJAMIN PHILLIPS. 

